This invention relates to a fuel supply system for direct injection engines and more particularly to an improved fuel supply system for an outboard motor incorporating a direct injection system.
As is well known, in all fields of engine design there is an increasing emphasis on obtaining more effective emission control, better fuel economy and, at the same time, continued high or higher power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the engine charge former. In order to obtain still further improvements, direct fuel injection systems are being considered. These systems inject fuel directly into the combustion chamber and thus have significant potential advantages.
In many applications, the incorporation of direct injection is relatively straightforward. However, in connection with outboard motors, the very compact nature of the outboard motor renders this further sophistication in engine design difficult to obtain.
The problems in connection with direct fuel injection systems for outboard motors is related primarily to the space that is.
These problems arise, in part, because of the number of components required for fuel injection and the very nature of some of these components. For example, with manifold injection systems for outboard motors, it has been the practice to provide a fuel injection system that includes at last the following components:
a low pressure fuel pump, PA1 a high pressure fuel pump, PA1 a pressure regulator, PA1 a vapor separator; and PA1 a fuel rail for delivering the fuel to the injectors.
The use of a vapor separator is required primarily because of the confined space and the fact that fuel vapors or air in the fuel, conditions primarily resulting from heat, can cause erratic injection and poor performance.
For the same reasons, it has also been the practice to position the high pressure fuel pump in the vapor separator so as to permit it being cooled and to minimize the amount of heat that is generated in the system and to remove the heat from the fuel that is delivered to the injectors. This also saves space. However, this necessitates the use of an electrically operated fuel pump. Such pumps have has limited capacity in the pressure which they can generate.
With direct injection systems, however, the fuel must be injected directly into the combustion chamber. This means that the pressure into which the fuel is injected is higher than with manifold injection systems wherein the pressure is at substantially atmospheric or even below. Electric pumps are not totally capable of supplying such high pressures.
In order to supply the necessary pressures for a direct cylinder injection, it has been proposed to employ a fuel supply system of the type used with manifold injection systems. This is comprised of an engine driven pump which supplies fuel to a vapor separator in which the electrically operated fuel pump is provided. However, fuel is supplied from this pump to a mechanical pump that is driven off of the engine and which can generate higher pressures as required by the direct injection system. This type of system can be quite effective.
Thus, it should be apparent that the utilization of high pressure fuel injection systems in outboard motors, although offering significant advantages, also magnifies the problem of component positioning and layout. More importantly, however, the various components of these systems are mounted relatively rigidly at spaced locations on various components of the engine and thus must be connected through flexible couplings. This give rise to complicated systems, ones which may be prone to leakage and also ones which have components that can deteriorate with age.
It is, therefore, a principle object of this invention to provide an improved fuel injection system for an outboard motor wherein the components are mounted together in such a way as to facilitate ease of assembly and to minimize the utilization of flexible conduits.
It is a further object of this invention to provide an improved fuel supply system for a direct injected outboard motor engine wherein many of the components can be attached together as a single assemblage for mounting on the engine to eliminate fitting problems, facilitate installation and avoid the number of flexible conduits that must be employed.